Great whites are among several species of sharks in Australian waters.
Photograph: Jim Abernethy/Getty Images/National Geographic

A surfer has died after losing both legs in a shark attack off the northern New South Wales coast, the second incident in as many days in the area.

Tadashi Nakahara, 41, was pulled from the surf at Shelly beach, a popular tourist spot in Ballina, at around 10am on Monday. He was given first aid but died on the scene.

It was the third fatal attack in New South Wales in the past 12 months and the sixth in Australia.

According to a local surfer, Allan Baldock, witnesses saw the shark appear to swim past others in the water to attack Nakahara, who was sitting on his surfboard about 10m from the beach.

“It went whack and he was thrown into the air ... it must have been a huge, huge shark,” Baldock told Guardian Australia.

Friends of the man, a Japanese national who had lived in the area for the past year, told a local cafe owner, named only as Karen, that the shark came out from nowhere. “It just came up between a bunch of surfers,” she said on Monday. “They weren’t even that far out.”

Shelley Beach in New South Wales, Australia, is closed after a Japanese surfer was killed by a shark

The victim’s friends were shaken up and looked “white as a ghost” as they carried his board away from the beach, the local said.

Lifeguards have since been stationed at all beaches in the Ballina Shire to keep people out of the water.

“This is obviously a very serious incident and we would ask that the public follow the directions of emergency service workers,” the NSW Surf Life Saving manager, Andy Kent, said.

Police boats scoured the water for the predator on Monday afternoon as marine scientists worked to identify its species and “determine whether that shark still poses a threat to humans”, police detective inspector Cameron Lindsay said.

Film crews had been stationed on the shore on Monday morning and may have captured video of the incident, he said. “We’re still looking at it, but what it appears to capture is a large amount of blood in the water.”

Lindsay hailed the surfers who brought Nakahara ashore and tried to save his life.

“I think their actions are commendable. Here we have a situation where [there is] a significant amount of blood in the water, they took to rescue this surfer, bring him in on shore.

“They did their best and unfortunately they couldn’t stop the blood loss.

“It’s obviously a stressful situation for them to go through.”

The Japanese consulate was working to inform Nakahara’s next of kin, police said.

Meanwhile another surfer is recovering in hospital after sustaining cuts to his lower back in a suspected shark attack on Sunday at nearby Seven Mile beach, close to Byron Bay.

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The 35-year-old was sitting on his board about 60m off the shore early on Sunday morning when he was struck from behind.

Neither he nor a friend saw what had attacked him. “I saw blood and I thought I’d better get back to shore,” he told the Seven Network.

Several beaches were also shut last week in Newcastle, on the state’s central coast, after lifeguards spotted a 1.8-metre shark near Bar beach.

The previous day a body surfer had emerged from another Newcastle beach, Merewether, bleeding from five puncture wounds to the left ankle sustained by a juvenile shark bite.

Newcastle’s beaches were closed for a record nine days in January after a spate of shark sightings, including a five-metre great white nicknamed Bruce.

A similar cluster of shark encounters gripped Australia’s west coast one year ago after three people were killed in the water. The West Australian state government responded by laying baited hooks near popular beaches, prompting nationwide protests and international outrage.

Shark nets stretch across 51 NSW beaches to keep the predators away. But studies suggest the nets, which mostly kill “non-target” animals such as turtles, dugongs and dolphins, have done little to stop human fatalities.

Daniel Bucher, a shark expert at Southern Cross University, warned against a shark panic in the wake of the attacks.

He said sharks traditionally made their way down the east coast during the summer. “Generally there are more sightings when the water’s warm, and that’s because the sharks hunt more actively, because they have higher metabolic rates,” he said.

Nonetheless, he said shark attack rates had remained relatively stable in the past 20 years, even as Australia’s population and tourist numbers had soared.

“You would presume the number of people in the water would also have increased, yet the number of people interacting with sharks hasn’t changed. That suggests the number of sharks in the water has actually gone down,” he said.

This story was amended on 9 February 2015 to correct the spelling of Tadashi Nakahara’s surname